1. Technical Field
The present invention relates to vehicle control systems, such as anti-lock braking systems and traction control systems. More particularly, the present invention relates to a vehicle control system that employs information from a vehicle steering system to provide the vehicle steering system with an enhancing input to adjust the steering of the vehicle to enhance the performance of the vehicle and the vehicle control system.
2. Discussion
The performance of vehicle control systems, such as anti-lock brake systems, traction control systems and stability systems is typically affected by several factors which the vehicle, control system is not configured to directly control and/or monitor. One such factor relates to a steering input transmitted to a vehicle steering system. As the vehicle control system lacks the ability to monitor and influence or control the steering input delivered to the vehicle steering system, the vehicle control system is not used to its fullest potential, with the result being relatively lower performance for both the vehicle control system and the vehicle.
One example of this problem is illustrated with reference to a vehicle having a conventional anti-lock brake system wherein the anti-lock brake system and the vehicle steering system are completely independent of one another. Because the anti-lock brake system lacks the ability to interact with the vehicle steering system, the anti-lock brake system is typically configured with a margin of safety to permit the vehicle operator to sharply maneuver the vehicle should it be necessary to do so while braking.
To provide this margin of safety, it is necessary to initiate the operation of the anti-lock braking system so that the braking force that is delivered is lower than the maximum possible braking force that the anti-lock braking system is capable of delivering. Successive iterations of an algorithm attempt to predict the manner in which the vehicle will be steered during the braking event so that the braking force delivered by the anti-lock braking system can be tailored to suit the anticipated need for tractive force to maneuver the vehicle. If it is determined that relatively little tractive force is necessary, the iterations of the algorithm may gradually increase the braking force that is delivered. Conversely, if it is determined that more tractive force is necessary, the iterations of the algorithm may gradually reduce the braking force that is delivered. In contrast to the conventional systems, a vehicle control system having means for directly monitoring the steering input provided to the vehicle steering system enables the vehicle control system to use real time data concerning the direction the vehicle is being steered, permitting the anti-lock brake system to immediately apply the maximum braking force for a given situation, as well as alter the braking force if the situation (e.g., steering input) is changed.
Another example of the above noted problem is illustrated with reference to a vehicle having a conventional traction control system wherein the traction control system and the vehicle steering system are independent of one another. Conventional traction control systems typically employ engine interventions wherein the flow of drive torque to the vehicle wheels is interrupted upon the detection of excessive wheel slip. While this approach can be successful, vehicle performance is adversely affected during the engine interventions.
In contrast to the conventional systems, a vehicle control system that directly monitors and controls or influences the steering input provided to the vehicle steering system enables the traction control to slightly alter the steering input delivered to the vehicle steering system to reposition of the vehicle wheels to increase traction without reducing drive torque. In this regard, the traction control system is able to maximize both traction and drive torque through the vehicle control system.
As another drawback, conventional vehicle control systems often operate in a less efficient manner due to their inability to directly control or influence the steering of a vehicle. Stability systems, for example, routinely rely on the independent and selective braking of the vehicle wheels to influence the direction of the vehicle. While this approach is effective, it is less efficient than altering the course of the vehicle by changing the steering input that is delivered to the vehicle steering system. This approach also increases the rate of wear for the components of the vehicle braking system.
It is one object of the present invention to provide a vehicle control system that is coupled to the vehicle steering system to provide the vehicle control system with data to improve its performance as well as that of the vehicle.
It is another object of the present invention to provide a vehicle control system which is able to analyze data on the vehicle""s path to tailor the performance of the vehicle control system in a manner which improves its performance.
It is another object of the present invention to provide a vehicle control system which is able to calculate a steering angle offset for changing the position of the vehicle wheels to improve the performance of the vehicle control system and the vehicle.
It is yet another object of the present invention to provide a method for controlling a vehicle using a vehicle control system.
In one preferred form, the present invention provides vehicle having a steering mechanism and a vehicle control system which cooperate to improve the performance of the vehicle and the vehicle control system. The vehicle also includes an input device adapted to produce a steering signal indicative of a manual steering input received from a vehicle operator. The steering mechanism has an input member operable for receiving a steering input and output member moveable in response to the steering input. The output member is positionable to control the direction in which the vehicle travels. The vehicle control system is operable for controlling a performance characteristic of the vehicle, and may include an anti-lock brake system, a traction control system or a stability system. The vehicle control system receives the steering signal and tailors its operation in response thereto. Preferably, the vehicle control system includes a control unit for selectively calculating a steering angle offset which is operable for causing the steering mechanism to reposition the vehicle wheels to further improve the performance of the vehicle control system and the vehicle. A method for controlling a vehicle is also provided.